Flow regulator and its use

ABSTRACT

The invention concerns a flow regulator, intended for gaseous substances, in particular for air in air-conditioning and ventilation installations, for maintaining the volumetric flow of the gaseous substance at desired magnitude with sufficient accuracy when the differential pressure acting across the flow regulator varies within desired limits. The flow regulator comprises an envelope and a regulating member disposed in the flow passage confined by the envelope. The flow regulator is provided with limiter members for limiting the differential pressure range of the flow regulator, said limiter members being disposed to restrict the movement of the regulating member. The limiters are adjustable and/or self-adjusting. The flow regulator has a scale for setting the limiter members.

BACKGROUND OF THE INVENTION

The present invention concerns a flow regulator for gaseous substances,in particular for air in air-conditioning and ventilation installations,for maintaining the volumetric flow of a gaseous substance at desiredmagnitude with sufficient accuracy, at a differential pressure acrossthe flow regulator varying within given limits, said flow regulatorcomprising an envelope and a regulating member disposed in a flowpassage confined by the envelope.

In low-pressure regulators known in the art, in which the set-pointvalue of volumetric flow can be regulated in a comparatively wide range,the lowest pressure at which the means starts to operate increases withincreasing volumetric flow. Even at small volumetric flow rates, thelowest pressure is generally relatively high. The top pressure alsoincreases in accordance with the set-point value of the volumetric flow.

Owing to the lowest pressure which is high and/or which depends on theset-point value of the volumetric flow, regulators of prior art, inorder to operate properly, require extra blower energy and potentially alarger blower; they have a great tendency to cause noise problems due topressure increase, or a need for damping; they impede the designing;they cause difficulties in the implementation phase of the installation.

As a rule, in flow regulators accurate and stepless setting of thevolumetric flow rate at the site of installation, particularly if theregulator has already been installed, is extremely cumbersome, and inpractice often impossible, nor can the set-point value of the volumetricflow rate be read directly. In regulators of prior art, the throttlingpressure with which the regulator throttles the flow cannot be readeither. It is true that in certain regulator designs of prior artdwelling within the operating range can be observed from the outside,but their volumetric flow rate cannot be regulated.

A prerequisite of serial manufacturing, storing, distributing and use ofthe regulator is that the regulators can with ease and accuracy beregulated at the site of installation even after installation. It isimportant in view of the balancing and inspection of an air conditioninginstallation that it is possible to observe from outside the regulatorwhich is the set-point value of the volumetric flow rate, whether theregulator is in the operating range, and how strongly the regulatorthrottles. In addition, the basic construction and manufacturingtechnique shall be such that the required calibrating measures are assimple and minimal as possible and independent of the setting of thevolumetric flow.

In regulators of prior art, the movement of the regulating member cannotbe steplessly limited. Therefore, regulators of prior art cannot be usedat all for mere balancing without incurring the risk of binding of themeans. Secondly, the regulators of prior art cannot be used forrestricted and controlled correction. Thirdly, regulators of prior artcannot be used in the best possible way in air-conditioninginstallations where the air quantities are varied, such as e.g.different air quantities in daytime and night running.

In regulators of prior art, for counterforce of the regulator member isemployed either a mass or a spring, or a spring and bellows incombination. Each of these designs has its advantages and disadvantages.Disadvantages when using springs are, for instance, relaxation of thespring, inaccuracies in manufacturing, susceptibility to damage, etc.Disadvantages of a mass used for counterforce have been that theregulator can only be installed in a horizontal duct, that the axisshould always be horizontal with reference to the direction of flow, andthat the mass must always be on the same side of the duct. Advantages ofa mass used for counterforce are, for instance, reliability in use, goodmanufacturing accuracy and constancy. Disadvantages of spring plusbellows are that the design is more prone to disturbances and moreexpensive than a mere spring, and has a shorter life span.

In regulators of prior art, for damping out the oscillations of theregulating member, or the so-called hunting, a particular damping meansis required. In certain designs of prior art, dashpot type damping isused. In another regulator of prior art, damping of bellows type isused. Disadvantages of the damping designs described above include thefact that the damping designs may bind in the course of time, or theymay be blocked or damaged, that the designs require maintenance, andthat they may impair the accuracy.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an improvement inregulator designs known in the art. A more detailed aim of the inventionis to provide a flow regulator in which the drawbacks present inregulators of prior art have been overcome.

The aims of the invention are achieved with a flow regulator which ismainly characterized in that the flow regulator is provided withlimiting members for limiting the differential pressure range of theflow regulator, said limiting members being disposed to limit themovement of the regulating member.

In an advantageous embodiment of the invention, the flow regulator ischaracterized in that the limiters are adjustable. In an advantageousembodiment the limiters are self-adjusting. In an advantageousembodiment the flow regulator is provided with a limiter setting scale.In an advantageous embodiment, the limiting members have been disposedto lock, if needed, the regulating member in any given position.

Several advantageous embodiments of the invention are characterized inthat the regulating member is a slightly curved plate. The turning anglebetween the initial and ultimate positions of the regulating member issubstantially of the same order at different volumetric flow rates whenthe differential pressure is the same. The operating range of the flowregulator is advantageously changeable by changing the effective flowaperture between the regulating member and the flow passage. Likewise,the operating range of the flow regulator is advantageously changeableby the aid of a shiftable mass producing a countertorque dependent onthe position of the regulating member.

With the flow regulator of the invention, several remarkable advantagesare gained, in the flow regulator of the invention, the movement of theregulating member may be restricted, or the movement of the regulatingmember may, if needed, be altogether arrested. Thanks to thischaracteristic feature, the flow regulator of the invention may also beused in designs such as balancing based merely on so-called single-passregulating, whereby no risk of binding of the means exists. Secondly,the flow regulator may be used for restricted and controlled correction,and thirdly, the flow regulator may successfully be used inair-conditioning installations in which there is a desire to change theair flows by centralized action.

Secondly, the flow regulator operates in a comparatively wide volumetricflow range, e.g. duct velocity 2-8 m/s, without changing the pressurerange in which the flow regulator operates. In addition, the flowregulator operates with lower differential pressure, e.g. about 20 Pa,than any regulator known in prior art, in which the operating range is20-200 Pa throughout the line. In the regulator of the invention, it hasbeen understood to utilize the turning angle of the regulating member ofabout 90°, whereby by regulating also the effective flow aperture alarge movement of the regulating member is achieved in proportion to thechange of differential pressures, and a relatively wide operating range.

Thirdly, in the flow regulator of the invention, the volumetric a flowrate may be regulated steplessly and simply of the site of installation,even if the regulator has already been installed in place, simply byturning the regulator knob on the flow regulator.

The volumetric flow rate may be read directly on the scale, as well ashow much the regulator throttles, and whether the regulator is in theoperating range, i.e., whether the correct air quantity is passingthrough the flow regulator, or too much or too little.

In the flow regulator of the invention, a mass is used advantageouslyfor counterforce. In the regulator of the invention, however, thedisadvantages of a mass have been eliminated in practice. The flowregulator of the invention may be installed in a passage running in anydirection, and the mass used for counterforce can be mounted on eitherside of the passage. This is due to the turning axis of the regulatingmember being installed horizontally by the aid of a levelling meansprovided in the flow regulator, and the mass is moreover so positionedthat the mass is turned an equal amount with reference to the regulatingmember, but in the opposite direction, as is the deviation in eachinstance from a basic installation.

The flow regulator of the invention also requires no separateoscillation inhibiting means, certainly no oscillation inhibiting meansliable to bind or gather dirt or to become blocked: in general, thecounterpressure in the passage alone will keep the regulating memberstable. The greatest contribution to this favourable feature comes fromthe fact that the regulating member is slightly curved, and that theregulating member does not nearly close the passage totally in anyposition. Therefore, air is enabled to flow past the regulating memberon all sides even when the regulating member is in its "closed"position. Other factors contributing to the favourable feature describedin the foregoing are, for instance, the size and shape of the regulatingmember, the position of the turning axis of the regulating member withreference to the regulating member, the size and location of thecounterweight, and the limiters of the regulating member.

Thanks to the slightly curved regulating member, the flow regulator canbe made accurate, silent, and a slightly curved regulating member likethis moves smoothly from one end position to the other.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in detail by referring to an advantageousembodiment of the invention presented in the figures of the drawingattached, but to which the invention is not meant to be exclusivelyconfined.

FIG. 1 presents an advantageous embodiment of the invention in a partlysectioned elevational view.

FIG. 2 shows the section along the line II--II in FIG. 1.

FIG. 3A presents an advantageous embodiment of the regulating memberused in the flow regulator of the invention, in schematical elevationalview.

FIG. 3B presents another advantageous embodiment of the regulatingmember used in the flow regulator of the invention, in schematicalelevational view.

FIG. 3C presents a third advantageous embodiment of the regulatingmember used in the flow regulator of the invention, in schematicalelevational view.

FIG. 3D presents a fourth advantageous embodiment of the regulatingmember used in the flow regulator of the invention, in schematicalelevational view.

FIG. 3E presents a fifth advantageous embodiment of the regulatingmember used in the flow regulator of the invention, in schematicalelevational view.

FIG. 3F presents a sixth advantageous embodiment of the regulatingmember used in the flow regulator of the invention, in schematicalelevational view.

FIG. 4A presents in elevational view the initial and ultimate positionsof the regulating member of the flow regulator, at high volumetric flow.

FIG. 4B presents in elevational view the initial and ultimate positionsof the regulating member of the flow regulator, at small volumetricflow.

FIG. 5A presents the effective flow aperture of the flow regulator ofthe invention at the smallest when the regulating member is so regulatedthat the effective flow aperture is large, viewed from the flowdirection.

FIG. 5B presents the effective flow aperture of the flow regulator ofthe invention at the smallest when the regulating member is so regulatedthat the effective flow aperture is large, viewed from the flowdirection.

FIG. 5C presents in elevational view the changing of the effective flowaperture of the flow regulator of the invention in a flow passage withvariable cross-section.

FIG. 5D presents in elevational view the changing of the effective flowaperture of the flow regulator of the invention by means of separateregulating member.

FIG. 6 presents the principle of limiting the differential pressurerange of the flow regulator of the invention, in schematic elevationalview.

FIG. 7 shows a detail of FIG. 6 viewed in the direction 6A.

FIG. 8 presents a mode of changing the operating range of the flowregulator of the invention, in schematic elevational view.

FIG. 9 presents the flow regulator of FIG. 1, seen in the direction fromthe cover of the protecting case, said cover being removed

FIG. 10 shows the operating range of the flow regulator of the inventionin graphic presentation.

FIG. 11 shows applications of the flow regulator of the invention ingraphic presentation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the embodiment of FIGS. 1 and 2, the constant flow regulator of theinvention is in general indicated by reference numeral 10. The regulator10 comprises an envelope 11 and a regulating member 12 disposed in theenvelope 11. In the present embodiment the regulating member is a curvedflap-resembling regulating member which is composed of two curved flaps12a and 12b placed to overlap. The regulating member 12 is attached to aturning shaft 13 with an adjusting and fixing nut 14 and with a combinedsleeve, adjusting and fixing nut 16.

The shaft 13 is rotatably carried in the envelope 11 by bearings 15 and18. The regulating member 12 turns in a flow passage defined by theenvelope 11 by action of the air flow, and a countertorque produced by aweight 23 has been disposed to place the regulating member 12 in aposition producing the requisite throttling effect. The weight 23 isintegrally connected to the regulating member 12 by mediation of thesleeve, adjusting and fixing nut 16 and of a member 19 rotatablyattached thereto and of a cover 20, and it turns along with the turningmovement of the regulating member 12. The shaft 13 is installedhorizontally by the aid of a levelling means and a levelling ball 31provided in the protecting case.

The operating range of the constant flow regulator 10 regardingvolumetric flow can be changed by turning the regulating knob 24,whereby in this embodiment the size of the flap-like regulating member12 and at the same time the effective flow aperture, the location of theweight 23 and the initial and ultimate positions of the regulatingmember 12 change. The halves 12a and 12b of the flap-like regulatingmember 12 move with reference to each other in different directions dueto the different-handed threads on the shaft 13 and in the adjustingnuts 14,16. One end of the shaft 13 has been locked sidewise in thebearing 15, whereby under effect of adjustment the member 19 rotatablyattached by means of the sleeve 16 to the flap-like closing member 12,to one half 12b thereof, as well as the cover 20 attached to said member19, moves axially with reference to the shaft 13. A gear 22 attached tothe cover 20 is in contact with the shaft 13, and the gear 22 is set inrotation by reason of the pinion rack constituted by the grooves on theshaft 13 and of the lateral movement of the rotatably disposed member19, whereby the gear 22 at the same time over the toothes rack 34 movesthe weight 23.

In FIGS. 3A-3F have been presented some advantageous embodiments of theregulating member employed in the regulator of the invention, 10. InFIGS. 3A-3D, the halves with reference to the turning axis 13 of theregulating member, 112a, 112b, 112c and 112d are slightly curved, whilein FIGS. 3E and 3F only one half of the regulating member 112e and 112fis slightly curved.

In FIGS. 4A and 4B is observed that at high volumetric flow rate, at thesmallest differential pressure of the operation range, the regulatingmember 12 is in a more horizontal position than at a small volumetricflow rate at the corresponding differential pressure.

Similarly, it is observed that at a small volumetric flow rate at thehighest differential pressure of the operation range, the regulatingmember 12 is in a more vertical position than at a large volumetric flowat the corresponding differential pressure.

The position of the regulating member 12 at the highest volumetric flowrate and at the smallest differential pressure of the operation rangeadvantageously deviates about 90° position of the regulating member 12at the smallest volumetric flow rate and the highest differentialpressure of the operation range. In contrast, the turning angle φ₂ issubstantially of the same order as the respective turning angle φ₁ forhigh volumetric flow rate when the differential pressure is the same.Thus, in the regulator 10 of the invention the rotation angle φ₁, φ₂ ofthe regulating member 12 for the minimum and maximum differentialpressures is substantially of the same order at different volumetricflow rates. At the same minimum and maximum values of the differentialpressure Δp, the angle of rotation φ₁, φ₂ is advantageously about 60°.

In the embodiment of FIGS. 5A and 5B, in the flow regulator 10 of theinvention the effective flow aperture 37 is changed by regulating thesize of the flap-like regulating member 12. In this embodiment, the sizeof the effective flow aperture 37 is changed by moving the halves 12aand 12b of the flap-like regulating member 12 in the manner indicated bythe arrow A in FIG. 5A.

In the embodiment of FIG. 5C, the effective flow aperture 37 is changedby moving the regulating member 12 in the flow passage 11, 11a withvariable cross-section as indicated by the arrow B, in other words, byshifting the regulating member 12 in the direction of flow.

In the embodiment of FIG. 5D, the effective flow aperture 37 is changedby regulating the flow aperture by the aid of a separate regulatingmember 36, consisting of one or several parts, placed in the flowpassage. The shafts of the regulating members 36 are denoted byreference numeral 35. The regulating members 36 may be rotated aroundthe axes 35 as indicated by arrows C.

In the flow regulator 10 of the invention, the differential pressurerange is limited by limiting members 25 and 26a, 26b. When the limiters26 are moved as indicated by arrows D in FIG. 6, the movement of theregulating member 12 is limited. The limiters 26 are advantageouslyself-regulating in accordance with the volumetric flow rate that hasbeen selected, as shown in FIG. 7. The limiters 26a and 26b havebevelled faces in that case. The limiters 26a and 26b regulatethemselves when a limiter pin 25 moves as the volumetric flow rate isregulated, in the manner indicated by the arrow E in FIG. 7. Themovement of the flap-like regulating member 12 of the constant flowregulator 10 may also be arrested totally or partially with the aid ofthe adjustable limiters 26a and 26b. The limiter pin 25 and theadjusting scale 39 on the protective case 32 indicate the differentialpressure Δp acting across the constant flow regulator 10. When thelimiter pin 25 touches the limiter 26a, the differential pressure Δp isat the lowest, and at the limiter 26b it is at the highest (FIG. 7).When the limiter pin 25 is intermediate between the limiters 26a and26b, the means is in the operating range; if not, either too much or toolittle air is admitted.

As shown in FIG. 8, the operating range of the flow regulator 10 can bechanged by the aid of a movable mass or weight 23 by shifting the weight23 as indicated by the arrow F.

The weight 23 and the limiting members 25 and 26a, 26b automaticallyassign different initial and ultimate positions to the flap-likeregulating member 12 at different volumetric flow rates.

In the constant flow regulator 10 of the invention the effect of gravitycan be made the same independent of the installation mode by the aid ofthe fixable cover 20 which is adjustable with reference to the turningaxle 13 of the regulating member 12, of the ball case 29 on theprotecting case 32 and of the ball 30 moving in the case 29. Theconstant flow regulator 10 is balanced by a balancing weight 38 inconnection with manufacturing without the countertorque produced by theweight 23. The ball 30 and the scale 40 on the case 29 show in whichposition the means is. The cover 20 is turned to a positioncorresponding to the position indicated by the ball 30 by the aid of ascale 41 on the cover 20 and is locked by a set screw 21.

The operating range of the flow regulator 10 of the invention regardingvolumetric flow rate V can be steplessly regulated so that thedifferential pressure range in which the flow regulator 10 operates willnot change, as presented in FIG. 10, or it can be made to change in anydesired manner. In FIG. 10, the hatched area indicates the range inwhich the flow regulator 10 of the invention operates. In the example ofFIG. 9, the ratio of the top and lowest pressures of the operating rangeis 1:10, or e.g. 20-200 Pa, and the ratio 1:4 of lowest and highestvolumetric flow rate V is such that it corresponds to air flow velocity2-8 m/s. The operating range of the constant flow regulator 10 isregulated, as already described, by turning the regulating knob 24. Thelimiter pin 25 on the rotatably disposed member 19, the limiters 26a,26b changeable in the direction of the shaft 13 and the weight 23 givethe regulating member 12 different initial and ultimate positions atvarious volumetric flow rates. The end of the gear rack 34 and thevolumetric flow rate scale 42 on the cover 20 indicate the air flow towhich the constant flow regulator 10 has been regulated. The limiter pin25 and the scale 39 adjacent to the limiter pin 25 on the protectingcase 32, in other words, the scale for setting the limiters 26a and 26b,indicate the differential pressure Δp across the regulator 10. If thelimiter pin 25 is against one or the other limiter 26a and 26b, the flowregulator 10 is not in the operating range, and too much or too littleair passes through the flow regulator 10. The position of the limiterpin 25 with reference to the scale 39 and the limiters 26a and 26b maybe determined from outside the means.

In the flow regulator 10 of the invention, the movement of theregulating member 12 may be restricted, or the regulating member 12 maybe completely arrested by the aid of the adjustable limiters 26a and26b, as was already presented above. This affords various possibilitiesas shown in FIG. 11.

The instance (a) displayed in FIG. 10 illustrates the case that theregulator 10 is only used for balancing an air-conditioninginstallation. When an air-conditioning installation is being balanced,the regulating member 10 automatically assumes the correct position.Thereafter, the regulating member 10 is arrested by means of thelimiting members 26a and 26b. The air-conditioning installation can bebalanced in this way with flow regulators, which means that the airquantities are correct at every point in the air-conditioninginstallation, but the regulators 10 installed in the air-conditioninginstallation do not strive to maintain the volumetric flow rate Vunchanged if it tends to change due to an external influence. The airflow may then be altered centrally. Since they have been arrested, theregulators 10 are also under no risk of becoming stuck.

The instance (b) displayed in FIG. 11 illustrates the case in which theflow regulator 10 is given a small chance of correction, e.g. ±20 Pa.The regulating members 10 assume the correct position at balancing. Theregulating members 12 of the flow regulators 10 are not completelyarrested with the limiters 26a and 26b in this case; the regulatingmember 12 is rather given a small latitude of movement in bothdirections. The flow regulator 10 will then in the event of minorpressure variations correct the volumetric flow rate if the magnitude ofthe volumetric flow tends to change. On the other hand, if for somereason the flow regulator 10 gets stuck, it will cause no major erroreven then.

The instance (c) displayed in FIG. 11 illustrates the case in which theair-conditioning installation is balanced with the largest air quantity.The flow regulator 10 is used in air-conditioning installations whereair flows of different magnitudes are used. Usually a higher volumetricflow rate is applied e.g. during the daytime. When balancing theair-conditioning installation, the movement of the regulating member 12is limited by the lowest pressure limiter 26a. One achieves hereby thatthe regulating member 12 prevents the increase of the air quantity inday operation but causes no problems whatsoever in night operation whenthe quantity of air is reduced by centralized action. If the regulatingmember 12 were allowed to turn to its fully open position, some point inthe air-conditioning system could in night operation receive nearly asmuch air as in daytime operation, and another point wouldcorrespondingly receive very little.

The instance (d) displayed in FIG. 11 illustrates the case in which theflow regulator 10 is used in air-conditioning installations where airflows of different magnitudes are used. The installation is balancedwith a smaller air quantity. The movement of the regulating member 12 ofthe flow regulator 10 is limited with the top pressure limiting member26b. The regulating member 12 cannot turn into its closed position, andthe regulating member 12 will thus cause no problems when the air flowis increased by centralized action.

The instance (e) displayed in FIG. 11 illustrates the case in which theflow regulator 10 is permitted to correct the air flow rate throughoutthe differential pressure range in which the flow regulator 10 operatessatisfactorily. The limiting members 26a and 26b are in their extremepositions.

In the foregoing are presented merely some of the advantageousembodiments of the invention, and it is obvious that variousmodifications may be accomplished in them within the scope of theinventive idea presented in the claims following below. For instance, itis not the intention to confine the invention exclusively to ducts orpassages having a circular cross section.

We claim:
 1. A flow regulator intended for gaseous substances, inparticular for air in air-conditioning and ventilation installations formaintaining the volumetric flow of a gaseous substance at desiredmagnitude with sufficient accuracy at differential pressure across theflow regulator varying within given limits, said flow regulatorcomprising an envelope and a regulating member disposed in a flowpassage confined by the envelope, characterized in that the flowregulator is provided with limiting members constituting means forrestricting the differential pressure range of the flow regulator, saidlimiting members being disposed to limit the movement of the regulatingmember, wherein minimum and maximum breadth of the differential pressureare arbitrarily determined by said limiting members.
 2. A flow regulatoraccording to claim 1, characterized in that the limiters are adjustable.3. A flow regulator intended for gaseous substances, in particular forair in air-conditioning and ventilation installations for maintainingthe volumetric flow of a gaseous substance and desired magnitude withsufficient accuracy and differential pressure across the flow regulatorvarying within given limits, said flow regulator comprising an envelopeand a regulating member disposed in a flow passage confined by theenvelope,characterized in that the flow regulator is provided withlimiting members constituting means for restricting the differentialpressure range of the flow regulator, said limiting members beingdisposed to limit the movement of the regulating member, andcharacterized in that the limiting members are self-adjusting when theset-point value of the volumetric flow rate is changed.
 4. A flowregulator according to claim 3, characterized in that the regulatingmember is disposed to turn when the differential pressure acting acrossthe flow regulator changes.
 5. A flow regulator according to claim 1,characterized in that the flow regulator is provided with a settingscale for the limiting members.
 6. A flow regulator according to claim5, characterized in that a limiting pin and said setting scale for thelimiting members are disposed to indicate the differential pressureacting across the flow regulator.
 7. A flow regulator according to claim3, characterized in that the operating range of the flow regulator ischangeable by changing the effective flow aperture between theregulating member and the flow passage.
 8. A flow pressure according toclaim 1, characterized in that the regulating member is substantiallyslightly curved at least on that flow surface which faces the incomingflow of the gaseous substance.
 9. A flow regulator according to claim 1,characterized in that the limiting members have been disposed to arrestthe movement of the regulating member altogether.
 10. The regulator ofclaim 1, wherein said regulating member is situated upon an axis anddisposed to rotate about said axis with increasing differential pressureprogressively crosswise with reference to the direction of flow.
 11. Aflow regulator intended for gaseous substances, in particular for air inair-conditioning and ventilation installations for maintaining thevolumetric flow of a gaseous substance at desired magnitude withsufficient accuracy at differential pressure across the flow regulatorvarying within given limits, said flow regulator comprising an envelopeand a regulating member disposed in a flow passage confined by theenvelope, characterized in that the flow regulator is provided withlimiting members constituting means for restricting the differentialpressure range of the flow regulator, said limiting members beingdisposed to limit the movement of the regulating member, additionallycomprisinga rotatable shaft upon which said regulating member issituated and disposed to rotate therewith; and a movable limiting memberalso situated upon said shaft and disposed to be movable with therotation thereof between positions defined by said limiting members,rotation of said regulating member being arrested when said movablelimiting member contacts one or the other of said position limitingmembers.
 12. The regulator of claim 11, wherein said positioned limitingmembers have bevelled faces.
 13. A flow regulator intended for gaseoussubstances, in particular for air in air-conditioning and ventilationinstallations for maintaining the volumetric flow of a gaseous substanceat desired magnitude with sufficient accuracy at differential pressureacross the flow regulator varying within given limits, said flowregulator comprising an envelope and a regulating member disposed in aflow passage confined by the envelope, characterized in that the flowregulator is provided with limiting members constituting means forrestricting the differential pressure range of the flow regulator, saidlimiting members being disposed to limit the movement of the regulatingmember, wherein a turning angle between initial and ultimate positionsof said regulating member is substantially of the same order atdifferent volumetric flow rates with the same differential pressure.